The present invention relates to new mercaptoacetamide compounds, compositions and methods for permanent hair shaping that are based on these new mercaptoacetamide compounds or their salts as keratin-reducing agents and methods for making these new mercaptoacetamide compounds.
The known classical method for performing permanent hair shaping is based on two treatment steps: in the first step the cystine-disulfide-bridges of the hair keratin are opened by action of a composition containing a reducing agent. Then the hair is put into the desired shape. In a second step the cystine-disulfide-bridges are again closed using a fixing composition, i.e. a composition containing an oxidizing agent.
Thioglycolic acid, e.g. as an ammonium or monoethanolamine salt, is used as classical permanent wave reducing agent, as disclosed in the pioneering work in German Patents 948 186 and 972 424. Additional common reducing agents include inorganic sulfite, 2-mercaptopropionic acid (thiolactic acid), 3-mercaptopropionic acid, certain mercaptocarboxylic acid esters, cysteine and derivatives of these compounds.
All these compositions however have a series of disadvantages. Alkaline adjusted preparations based on mercaptocarboxylic acids, in spite of sufficient action, produce hair damage which manifests itself for example in increasing hair strand breaks. Furthermore these compositions load the scalp skin in an undesirable manner.
Finally the unpleasant smell of the reducing agent used requires an intensive perfuming of the product. Several of these problems however can be solved by using 2-mercaptopropionic acid (thiolactic acid). Generally thiolactic acid is characterized by a weaker shaping action than most of the other thioglycolic acids.
Mercaptocaroxylic acid esters which have hair shaping action even at reduced pH values, are unsatisfactory in regard to their skin compatiblity and their risk of sensitization. Instead of mercaptocarboxylic acid ester mercaptoacetamide compounds, such as thioglycolic acid amide or alkyl or hydroxyalkyl substituted amides, have also been used. Compositions of this type are disclosed in International Patent WO-A-91/10421 and European Patent EP-A-0 455 457. These materials have, like the carboxylic acid esters, highly effective shaping power, also at low pH values, however they are criticized even more than the esters in regard to their sensitizing action.